Corn Investigation

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# Corn Investigation - PowerPoint PPT Presentation

Corn Investigation. Count the number of kernels that are: yellow &amp; smooth, yellow &amp; wrinkled , purple &amp; smooth, purple &amp; wrinkled. Reduce this ratio to lowest terms (it is okay to have decimals in your answer) What type of inheritance are you examining? (Monohybrid or Dihybrid )?

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Corn Investigation
• Count the number of kernels that are: yellow & smooth, yellow & wrinkled, purple & smooth, purple & wrinkled. Reduce this ratio to lowest terms (it is okay to have decimals in your answer)
• What type of inheritance are you examining? (Monohybrid or Dihybrid)?
• Based on the ratio from Q1, what could the possible genotypes of the parents be? (hint: do not do a punnett square. Look at the ratio to help you figure out the parents)
• You are modelling how Mendel recorded data. Is counting an effective way to collect data? Why? What is one experimental error that could have occurred? (Hint: counting wrong is not an error)
Beyond Mendel
• Mendelian Genetics deals with inheritance patterns that show complete dominance
• Meaning, the dominant allele completely masks (overpowers) the expression of the recessive allele
• Are inheritance patterns in nature always this simple?
Incomplete Dominance
• A situation where neither of the 2 alleles are dominant over the other.
• Phenotype of heterozygote is a BLEND of the two alleles.
• Alleles are written using a superscript letter (ex. CR = Red)
• Example: snapdragons (see picture)
Codominance
• Both alleles are dominant, and thus fully expressed in the heterozygote
• Exhibited in a heterozygousindividual where both alleles of a gene are expressed, not blended.

Sickle Cell Anemia (blood disease)

Cow coat

Impatien flowers

Examples of Co-Dominance

Talk to me when there’s meat… meeow!

Examples:

• black cat x tan cat = Tabbycat (black and tan stripes)
• Roan coat in horses (white and red hair)
Multiple Alleles
• So far, the inheritance examples we have looked at only have 2 alleles
• Example: Brown hair or blonde hair, brown eyes or blue eyes, etc.
• Most traits in nature are controlled by more than 2 alleles, such as human blood groups
Multiple Alleles
• When more than 3 phenotypes are possible, then more than 2 alleles for that trait must exist in the population.
• However, individuals have only two of those alleles.

Why?

• Because only one allele is inherited from each parent
Example of Multiple Alleles
• The ABO system of human blood type involves three alleles (IA, IB, and i).
• IA and IB – co-dominant, where “i” is recessive
• As a result, there are four possible phenotypes or blood types: A, B, AB, and O.
What do the Alleles Code For?
• The blood types differ due to the molecules that are present on the outside of the red blood cells (antigens)
• Antigens act as recognition factors for our immune system

Type A

Type AB

Type B

Type O

What do the Alleles Code For?

Both A & B

No antigens

What do the Alleles Code For?
• When white blood cells do not recognize the antigen, it considers the cell an invader and produces antibodies to attack that cell
• This is why receiving an incorrect blood type will cause agglutination (clumping).
Human Blood Groups: Multiple Alleles AND Codominance
• Human blood types are controlled by a single gene (expressed as an antigen: protein on surface of red blood cell)
Example
• If a man has type AB blood and his wife has type A blood (heterozygous), what are the possible blood types of their children?